Chinese chestnut did not induce negative plant soil feedback during centuries of growth

Certain tree species can reach ages of centuries, whereas lifespan of species like apple are markedly shorter. The latter is caused by negative plant-soil feedback that results in microbiome changes. We hypothesized that tree species with a long lifespan will be able to avoid such negative feedback and their root-associated microbiomes will be similar in trees of different ages. To test this, we used Chinese chestnut (Castanea mollissima) trees, ranging from 8 to 830 years old from a Ming orchard at the Great Wall. Their root-associated microbiomes were analysed by using meta-amplicon sequencing analysis. Their root-associated bacterial microbiomes were rather similar although based on linear regression models we cannot exclude that age has a weak correlation with microbiome compositions. When chestnut seedlings were grown for 3 months in soil associated with young or old trees, the plants were healthy and their growth was similar. This strongly supported that negative feedback had not occurred. Pseudomonas OTU1, a member of the core microbiome and representing >50 % of the rhizosphere community, strongly inhibited growth of chestnut pathogens and stimulated plant growth. Such properties of the microbiome, in combination with a high number of resistance genes can contribute to longevity of chestnut.